Lense using TotallyLazy

gistfile1.java

import com.googlecode.totallylazy.Function1;
import com.googlecode.totallylazy.Function2;

public class Lenses {
    public static void main(String[] args) throws Exception {
        Person rhys = new Person("rhys", 33, new Address("2 east lane", new Postcode("se16", "4uq")));

        Person older_rhys = Person.lenses.age.set(34, rhys);
        System.out.println(older_rhys);

        Person rhys_at_e1 = Person.lenses.postcode.set(new Postcode("e1", "1aa"), rhys);
        System.out.println(rhys_at_e1);
    }
}

class Person {
    final String name;
    final int age;
    final Address address;

    Person(String name, int age, Address address) {
        this.name = name;
        this.age = age;
        this.address = address;
    }

    public String toString() {
        return name + ": age=" + age + ", address=" + address;
    }

    public static class lenses {
        public static final Lense<Person, Integer> age = Lense.lense(functions.age, functions.setAge);
        public static final Lense<Person, Address> address = Lense.lense(functions.address, functions.setAddress);
        public static final Lense<Person, Postcode> postcode = address.then(Address.lenses.postcode);
    }

    public static class functions {
        public static final Function1<Person, Integer> age = new Function1<Person, Integer>() {
            public Integer call(Person person) throws Exception {
                return person.age;
            }
        };
        public static final Function2<Integer, Person, Person> setAge = new Function2<Integer, Person, Person>() {
            public Person call(Integer newAge, Person person) throws Exception {
                return new Person(person.name, newAge, person.address);
            }
        };
        public static final Function1<Person, Address> address = new Function1<Person, Address>() {
            public Address call(Person person) throws Exception {
                return person.address;
            }
        };
        public static final Function2<Address, Person, Person> setAddress = new Function2<Address, Person, Person>() {
            public Person call(Address newAddress, Person person) throws Exception {
                return new Person(person.name, person.age, newAddress);
            }
        };

    }
}

class Address {
    final String street;
    final Postcode postcode;

    Address(String street, Postcode postcode) {
        this.street = street;
        this.postcode = postcode;
    }

    public String toString() {
        return street + " " + postcode;
    }

    public static class lenses {
        public static final Lense<Address, Postcode> postcode = Lense.lense(functions.postcode, functions.setPostcode);
    }

    public static class functions {
        public static final Function1<Address, Postcode> postcode = new Function1<Address, Postcode>() {
            public Postcode call(Address address) throws Exception {
                return address.postcode;
            }
        };
        public static final Function2<Postcode, Address, Address> setPostcode = new Function2<Postcode, Address, Address>() {
            public Address call(Postcode newPostcode, Address address) throws Exception {
                return new Address(address.street, newPostcode);
            }
        };
    }
}

class Postcode {
    final String outward;
    final String inward;

    Postcode(String outward, String inward) {
        this.outward = outward;
        this.inward = inward;
    }

    public String toString() {
        return outward + " " + inward;
    }
}

class Lense<A, B> {
    private final Function1<A, B> get;
    private final Function2<B, A, A> set;

    private Lense(Function1<A, B> get, Function2<B, A, A> set) {
        this.get = get;
        this.set = set;
    }

    public static <A, B> Lense<A, B> lense(Function1<A, B> get, Function2<B, A, A> set) {
        return new Lense<A, B>(get, set);
    }

    public A set(B b, A a) {
        return set.apply(b,a);
    }

    public <C> Lense<A, C> then(final Lense<B, C> other) {
        return lense(
                get.then(other.get),
                new Function2<C,A,A>() {
                    public A call(final C c, final A a) throws Exception {
                        return set(other.set(c, get.apply(a)), a);
                    }
                }
        );
    }
}